1. Field of the Invention
One embodiment of the present invention relates to a secondary battery. The present invention relates to an object, a method, or a fabricating method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. Furthermore, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, an imaging device, a power storage device, and a method for driving them, or a method for fabricating them. In particular, one embodiment of the present invention relates to an electronic device.
Note that electronic devices in this specification mean all devices including secondary batteries, and electro-optical devices including secondary batteries, information terminal devices including secondary batteries, vehicles including secondary batteries, and the like are all electronic devices.
2. Description of the Related Art
In recent years, portable information terminals typified by smartphones have been actively developed. Portable information terminals, which are a kind of electronic devices, are desired to be lightweight and compact.
As an example of a wearable device with which information can be obtained visually without using hands at any place, Patent Document 1 is disclosed. Patent Document 1 discloses a goggle-type display device that includes a CPU and is capable of communication. The device disclosed in Patent Document 1 is also a kind of electronic device.
Most wearable devices and portable information terminals include secondary batteries that can be repeatedly charged and discharged, and have problems in that there is a limitation on the time for operation because their light weight and compactness limit the battery capacity. Secondary batteries used in wearable devices and portable information terminals should be lightweight and compact and should be able to be used for a long time.
Examples of the secondary battery include a nickel-metal hydride battery and a lithium-ion secondary battery. In particular, lithium-ion secondary batteries have been actively researched and developed because capacity thereof can be increased and size thereof can be reduced.
Electrodes serving as positive electrodes or negative electrodes of lithium-ion secondary batteries are each formed using, for example, lithium metal, a carbon-based material, or an alloy material.